LONDON — The British police arrested 14 men in south, east and north London overnight, raiding a halal restaurant and an Islamic school in the latest display of concern about the spread of potential terrorists among British Muslims, police officials said Saturday.

Separately, the police in Manchester in the northwest said they arrested two men in raids on three homes on Saturday morning. None of the arrests were linked to the huge security alert that began Aug. 10 when police rounded up 24 people to thwart what they called a terrorist suicide plot to bomb trans-Atlantic airliners, police officials said.

At that time, the British authorities had raised their terrorism threat assessment level to "critical," the highest designation meaning that an attack was imminent. That was reduced four days later to "severe," meaning that an attack was "highly likely." The threat assessment level remained at "severe" on Saturday, according to the British MI5 Security Service Web site.

There was no immediate indication from the police that the latest arrests were related to a specific conspiracy such as the one described by the authorities on Aug 10. A police official, who spoke in return for anonymity because the investigation was continuing, said one line of inquiry was whether those arrested had been seeking to set up training facilities for would-be terrorists.

Word of the latest raids in London began to emerge late Friday after as many as 50 officers stormed into the Bridge to China Town restaurant on Borough Road, south London. People living nearby said the restaurant was crowded at the time and was generally popular with Muslims because it serves halal food permissible under Islamic dietary laws. The police did not say what the men were suspected of doing.

Referring to the number of police officers, the restaurant owner, Madi Blyani, told the British Broadcasting Corporation: "It was surprising, actually, because plenty of them suddenly came in all together. There were more than 50 or 60 of them. They suddenly came inside because they were suspicious of some of the customers, and they talked to them. They talked to them more than one hour, two hours. And they arrested some of them."

A police statement on Saturday said the 14 men arrested in London had been seized under counterterrorism laws "on suspicion of the commission, preparation or instigation of acts of terrorism." Police officers declined to go into detail on Saturday about their search of a privately financed Islamic school in the village of Mark Cross, near Crowborough, south of London, but said it was linked to the overnight raids.

Last Sunday, a British tabloid, The Express on Sunday, reported that Abu Hamza al-Masri, a radical Islamic cleric imprisoned this year on charges of inciting racial hatred and soliciting murder, had sought to use the Jameah Islameah Islamic school at Mark Cross, which offered weekend camping sites for Muslims. It quoted the school's imam, Bilal Patel, as saying Masri and a group of followers had camped on the school's 54-acre grounds but had been asked not to return. The newspaper did not say when Masri had used the school.

"We had to tell Abu Hamza that we did not want him to come again because he was so strange," Patel was quoted as saying. "He had given me a letter explaining some of his views, and I passed that on to the local police. Later on I was visited by some people from the security services. I assumed they were from MI5 because they asked an awful lot of questions but they didn't really say who they were."

According to figures released in 2005, the vast majority of Britain's 7,000 publicly financed religious schools were Christian, in addition to 36 Jewish, 5 Muslim and 2 Sikh schools. But there are also around 120 private Islamic schools.

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"The arrests in south and east London follow many months of surveillance and investigation," the police statement said.

The raids began only hours after Peter Clarke, the chief of London's counterterrorism police, was quoted as saying that thousands of terrorism suspects may be at large in Britain - a figure certain to alarm those in the United States who have taken to depicting some among Britain's 1.6 million Muslims as a growing security threat.

For instance, an article in August in The New Republic carried a headline calling London "Kashmir on the Thames" and said, "In the wake of this month's high-profile arrests, it can now be argued that the biggest threat to U.S. security emanates not from Iran or Iraq or Afghanistan, but rather from Great Britain, our closest ally."

Clarke said, "What we've learned since 9/11 is that the threat is not something that's simply coming from overseas into the United Kingdom." He was speaking in an interview, recorded in July, that is to be broadcast Sunday as part of a BBC program tracing links between British and foreign terrorists.

"What we've learned, and what we've seen all too graphically and all too murderously is that we have a threat which is being generated here within the United Kingdom," Clarke said.

He declined to say how many people were under suspicion, but said, "All I can say is that our knowledge is increasing and certainly in terms of broad description, the numbers of people who we have to be interested in are into the thousands."

He added, "That includes a whole range of people, not just terrorists, not just attackers, but the people who might be tempted to support or encourage or to assist."

In the latest raids, the police in Manchester said they seized two men at 6 a.m. Saturday, linking the arrests to the detention of a third man in the same area on Aug. 23.